COLD CRYSTALLIZATION OF POLY (ETHYLENE TEREPHTHALATE)
In order to clarify polymer conformations prior to crystallization, crystallization behavior of poly(ethylene terephthalate) (PET) from a quenched, amorphous state has been examined. The crystallinity of the samples annealed in the low temperature range 130°C to 180°C was nearly constant at ca. 40%, supporting a model similar to Yeh's folded chain fringed micellar grain model but without local orientation of the segments. IR measurements (CH2 rocking and CO stretching) showed that the content
... that the content of trans -CH2 -CH2-bond was as low as ca. 10% in the original sample, indicating the existence of quite local bends in the PET chains in the amorphous state. Tg, as determined by dilatometery as a function of the annealing temperature, showed an abrupt drop at 170°C, indicating the destruction of the "fringed micellar'network". Weight loss vs time curves during treating the samples by monoethylamine also reflected the destruction of the "network" and the formation of new lamellar crystals at higher temperatures than 170 C. Finally, DSC measurements of samples before and after treating by the amine, suggested that the small peak appeared at ca. 160°C for the sample annealed at low temperatures (120°C -160°C) may be due to the melting of the crystals formed in the grain boundary proposed by Yeh.